communicate between plug-ins in different sandboxes

Given that there are many cases where it is necessary to communicate between plug-ins in different sandboxes, what can we do?

1. We can communicate through a shared data structure or event passing system that lives in a sandbox   that is a parent to both plug-ins. You can create your mechanisms to do this, or you can use the event system .
Note: It’s important to remember that event classes send via the event system  must be either defined in the JRE core library (java.lang.String, for example) or in a parent sandbox.

2. A class in a parent sandbox can invoke call methods on a class in a child sandbox through an interface. The interface must be defined in the parent sandbox (which makes it visible to both parent and child). A class in the child sandbox can then implement the interface and register that implementation with the parent. Finally, the parent can make calls to the child via the interface.